Re: [Bug-gsl] Bug in sys/ldfrexp.c

From:

Brian Gough

Subject:

Re: [Bug-gsl] Bug in sys/ldfrexp.c

Date:

Mon, 29 Oct 2007 21:37:43 +0000

User-agent:

Wanderlust/2.14.0 (Africa) Emacs/22.1 Mule/5.0 (SAKAKI)

At Sat, 27 Oct 2007 19:47:12 -0400,
Chris Mihelich wrote:
> I wish to report and correct the following bugs in sys/ldfrexp.c:
>
> (1) gsl_ldexp computes a power of 2 (p2) that may overflow or
> underflow even though the correct answer is representable;
> consequently the return value x * p2 may be spuriously zero or
> infinity.
>
> (2) gsl_frexp can hang (this is what bit me in the rear at work
> yesterday) if its call to gsl_ldexp spuriously returns zero or
> infinity as in (1). The first while loop divides infinity by 2.0 over
> and over and wonders why it doesn't get any smaller; the second while
> loop has an analogous problem with zero.
Thanks for the bug report and code. I will fix those problems for
the next release.
--
best regards,
Brian Gough
(GSL Maintainer)
Network Theory Ltd,
Commercial support for GSL --- http://www.network-theory.com/gsl/